This invention relates to effluent water filtering systems and more particularly relates to an effluent water filter device, which is easy to install and maintain.
In present effluent water filtering systems, most suspended solids, bacteria and other organisms are filtered out by passing the water through a bed of sand sometimes layered on top of pulverized charcoal or through a matrix of fibrous materials. Some of these types of filters are known as "slow sand filters" and may range in size from a fraction of an acre in some small plants to several acres in large plants. The water is passed through these systems at a relatively low rate. The sand used in these filter systems is usually a fine sand, which clogs with use and thin layers of the dirty sand must be scrapped from the filter periodically to maintain capacity. The disadvantages of these types of filter systems, are the large area required in addition to the labor needed to clean the filters and handle the filter sand.
More often, the filtering systems presently in use are rapid sand filters, which is made possible by coagulation and sedimentation before filtration to remove the heaviest part of the load. These systems use a fairly coarse sand and include facilities for backwashing the filter to keep the bed clean. The filter beds are generally small ranging from 150 square feet in some small plants to 1500 square feet in larger plants. The filters themselves consist of a layer of sand or occasionally crushed anthracite coal up to two (2) feet deep resting on graded layers of gravel above an underdrain system. Maintenance of these systems is difficult and requires a great deal of labor. These type filters are generally built in concrete boxes or open tanks of wood and steel. The flow through the filter is generally by gravity or the water may be forced through the sand under pressure by pumping. However, excessive pressure frequently causes turbidity and bacteria may appear in the discharge water. Thus, pressure filters are not favored because they are difficult to inspect and keep in good order, thus, open gravity filters are favored for public water supplies. Even these, however, do not always filter out some of the harmful bacteria, carcinogens and cancer-causing agents.